How to prep, in 7 steps, for Google's mobile search change

Here's what to do before Google's mobile-friendly algorithm kicks in April 21.

Also check your website's search results ranking on non-mobile devices. Google has noted that a site could be downgraded across the board.

If, for instance, a website isn't mobile-friendly and drops in mobile search rankings, it may also drop in desktop rankings, too.

7. Test. Test. Test. Of course, if you're making changes to your site, you need to test it a lot. Don't test it once and assume you're good to go. Test repeatedly and from different kinds of devices a desktop, and variety of smartphones and tablets.

Also make sure that your big changes and small tweaks are working across all platforms.

"If you still do not have a responsively designed/mobile-friendly website, you better get on it, and get on it fast," said Collin Colburn, an analyst at Forrester. "But this is something that you should have -- if you have not already -- been working on."